‘I don’t know who the perpetrator is. It just seems so unlikely that Ross of all people would be capable of carrying out such complex murders without leaving a trace of himself behind. I said the same thing to Berlin, and she told me I had no respect for more experienced police officers, but please believe me – that’s not what I meant.’

‘Of course not. It’s a long time since we had that kind of discussion.’

Alex wanted to get back to Spencer, explain why he’d said what he had. But he was caught up in Fredrika’s assertion that Ross was an unlikely candidate. Was he too old, too unsophisticated, or had they underestimated him? Ross with his stooped posture, his Wellingtons. Who knew what he was capable of, what was concealed behind the façade.

‘We can’t ignore the fact that he managed to abduct an entire family and keep them off the radar for two months. That’s quite an achievement.’

Fredrika shook her head.

‘He didn’t build that house, Alex. His revenge was served up on a plate; all he had to do was kidnap the family. And he didn’t have to be particularly careful, because he didn’t expect anyone to start looking for them. They were supposed to be in Australia.’

Good point.

‘So what have we missed?’ Alex said. ‘What do you want to take a closer look at?’ This gave him another chance to talk about Spencer.

‘The man who bought the books,’ Fredrika replied.

‘The man whose voice wasn’t Ross’s.’

Alex touched the scars on his hands for the thousandth time. Henry Lindgren’s death was the most terrifying of them all. A crystal-clear link to the past, to one of Alex’s failures as a police officer.

‘I’m not sure, Fredrika. We can be absolutely certain of two things: the man in question knows me, and he’s familiar with the background of his victims on a level of detail I find absolutely horrific. Who else fits those criteria, apart from Ross? Who else have we managed to link to all the victims, apart from Ross?’

Fredrika thought for a moment.

‘No one,’ she admitted eventually. ‘On the other hand, we haven’t looked very hard. We can’t rely on the principle that “it can’t be anyone else”. That’s not evidence, and it won’t stand up in court.’

‘I’m well aware of that, thank you.’

Alex hadn’t meant to snap, but Fredrika withdrew into herself, closed down.

‘My apologies,’ she said.

Silence.

Fredrika, I know.

They had to talk about the letter, about Spencer.

‘What was Ross like when he was younger? Was he good at his job?’

The question sent Alex spinning back through the decades, made him think about all those years that had disappeared, all the capabilities that had dwindled.

‘He was one of the very best,’ he said hoarsely.